Businesses, institutions, government agencies, common carriers, and value-added service providers utilize packet-switched networks that integrate frame-delimited data traffic (including frame relay), packetized speech, and constant bit rate (non-delimited) traffic onto common transmission facilities. For such networks, a basic unit of transmission has been defined to be a "fast packet." A fast packet typically contains a header that includes connection identification and other overhead information, and is fixed or restricted in length (e.g., to contain a "payload" of 48 octets of user information). Where is it necessary to convey information of length greater than that of a maximum payload size, a fast packet adaption protocol is utilized, operating at a higher level than a fast packet relaying protocol, where the fast packet adaption protocol includes a segmentation and reassembly function. It is useful to note that transmission of integrated packets requires congestion control because of its bursty nature, while transmission of constant bit rate (CBR) traffic does not require such control.
Packet switched networks are subject to congestion when traffic offered to the network exceeds a capacity of the network. Such congestion is random in nature. End-user equipment tends to offer traffic in "bursts," interspersed with periods of inactivity. Networks are typically designed to accommodate some expected aggregate offered load. However, cost to an operator of the transmission network facilities and related equipment increases as the capacity of the network. Thus, networks are often designed to accommodate less than an absolute maximum possible offered load, and to rely on statistical effects to avoid blocking of transmission. Such a design may lead to congestion.
During occurrence of congestion, queues internal to nodes that constitute the network grow, and may exceed the memory allocated to them, forcing packets to be discarded. In addition, the end-to-end transit delay experienced by packets traversing the network increases significantly as offered traffic increases. Discarding of packets and increased end-to-end transit delay degrades an end-user's perceived quality of service. In addition, discard or excessive delay cause commonly used end-to-end protocols to retransmit not only those packets which were discarded or delayed, but all packets which were unacknowledged at a time that the discard or time-out was determined. This typically results in an avalanche effect, during which the network ceases to perform useful work and cannot recover without manual intervention.
In a "connection-oriented" packet network, values of quality-of-service parameters are negotiated among originating end-user equipment, the network(s), and terminating end-user equipment. Categories of negotiated parameters include throughput and transit delay. Throughput parameters typically describe the users' expectations of traffic to be offered during a given time period, an estimation of a greatest amount of traffic the users expect to offer during such a period, and a metric for describing "burstiness" of traffic. This throughput information is used by the network(s) for purposes such as resource allocation and rate enforcement.
There is a need for a device and method for providing a rate-based congestion control for integrated packet networks that performs rate enforcement such that end-user equipment may exceed an expected throughput agreed during negotiation, utilizing the network(s) on a space-available basis when capacity is available in the network(s).